I guess I am an optimistic realist. Travel to Mars or even the Moon in the next 10-20 years will probably not attract profit minded investors, but suborbital joy rides will. Thousands of people have already paid tens of thousands of dollars each to do things like climb mount Everest, fly to the south pole and ride in a Mig 25. 7000 people have already told Virgin Galactic they will pay $200,000 for a ride in SS2. Over the next few years suborbital flights will go higher and faster for less money until in 10-20 years we will have affordable commercial orbital tourism. From low earth orbit to a free return swing around the Moon will follow pretty quickly after that. Unfortunately I don't see tourism on the Surface of the Moon becoming routine in my lifetime. Fortunately, Burt Rutan does.

It will become less expensive to supply Oxygen, and other consumables, from the Moon to LEO and other near Earth locations than to lift these materials directly from the Earth. It is not difficult to liberate Oxygen from lunar crustal material using solar heat and solar electric power. Combined with lightweight Hydrogen, which might be transported from the Earth ( if not produced from Polar Ice on the Moon) this reduces the “Earth Lift Mass” necessary for Earth/Moon transport of materials. An Oxygen/Liquid Aluminum motor is also possible for operations near the Moon itself, using only lunar materials for fuel. These and other uses will support a resident community on the Moon.

There seems to be a sign at the horizon that there really are chances. As the article "Mogul eyes Space Coast for rocket’s maiden mission" ( www.xprizenews.org/index.php?p=740#more-740 ) says, Elon Musk first wanted to develop a Mars rover costing not more than 20 million $. The reason to develop rockets having low launch costs is that the launch of his 20 million $-Mars rover would have cost 50 million $. This he is reducing down to 20 million and less it seems.

So perhaps he might launch his private Mars rover one day. If he will really do that then this would mean that martian industry is realistic as well as mining asteroids because Musk would have proven that a small private company like SpaceX can send a robot to Mars. A much larger company would be able send several rovers or large rovers or a mix of rovers and vehicles to return the arch.

But - closer to us - it would prove mining the moon to be realistic seen from Economics too.

Cadet wrote (8/12/04) “Think about it. A plane ticket costs about a dollar per pound. Do you really think you can get to orbit that cheaply? “

The absolute minimum energetic cost of reaching LEO = 2000 miles (1/2 Earth radius) of lift (at constant, sea level “1 g” force/mass). Earth escape doubles this to 4000 miles equivalent. A good airplane can go 10 miles for the energetic equivalent of 1 mile climb. (The optimum L/D is 20:1, but I’ll use a more realistic number). This makes orbit energetically equivalent to 20,000 mile, approximately “round the world” flight. This is a nice comparison, since orbital passengers will expect to go around the world at least once.

Rockets have a surprisingly high thermodynamic efficiency – over 64% at a mass ratio that could get you into orbit (with Hydrogen and Oxygen). With much cheaper LOX plus kerosene the efficiency for orbit is still over 40%, using about 20 pounds of fuel for each payload pound. With this fuel at about $ 0.20 per pound (bulk, no tax), this gives $4.00 per pound to orbit. If you leave your RV at home, you could get to orbit for $800.

The quoted airline ticket cost is not for a globe circling trip. This would cost several dollars per pound ( and use about 40 pounds of fuel per pound of payload, since aircraft engines don’t get 40% efficiency). I understand that AVERAGE pricing (not seat-filler specials) for airlines is only 2 to 3 times the fuel cost. In any case, the costs could be comparable.

Note concerning space elevators: What a great idea! BUT, you don’t get to orbit, and don’t get to speed around the planet. You pay to approach “escape” altitude, even if you would rather not. You are going to need extremely efficient generators and motors to meet the energetic efficiency of rockets, and the first cost is daunting! (OK, no-one goes up until someone else comes down, thus net zero energy, “except for friction losses”).

Next Note, you use the elevator lower Moon rocks and other materials to ground for net power output. OK, but an orbital electromagnetic decelerator can extract a lot of energy from “mined minerals” without this tricky hardware.

Do I know how to do spaceflight at the calculated price? NO WAY! Do I want to think about this question? Not particularly. I think about pioneers, not vacationers. In 1850 a successful small businessman (usually a farmer) could liquidate his property and pay to relocate his family to the American west coast. Many found this to be a good move. In today’s terms this would involve over a million American dollars. This permits a transportation cost about 100 times greater than the fuel cost for rocket flight, and can thus be accomplished sooner.

Sorry about the out of date posting, I am out of sync in many ways. RPS

Thank You Very Much for that post. It seems to be assisting my thoughts.

Concerning the space elevator I suppose that Edards did extend it it - in his concept - to 100,000 km altitude to meet the disadvantages you mentioned. The disadvantages are the to low velocities got by the elevator below 36,000 km altitude. payloads released below 36,000 still require acceleration and thus propellant. Or the payloads for LEO are released above 36,000 and decelrated then which again requires propellant unless electromagnetic deceleration is used - you mentioned this idea.

But for the expensive interplanetary flights - unmanned as well as manned - there would be advantages.

The economical advantages of the space elevator depend on two markets at least - LEO launches and interplanetary launches. There may be growth of interplanetary missions within a decade from now because of the Bush plan as well as because of evolutions of private spacflights. It's again a topic of economies of scale as well as of those of scope.

It will be very interesting to watch that.

From my point of view all these things and topics are elemants and components of a larger whole ínfrastructure - it is problematic if not impossible to evlaute each element isolated from the others I suppose.

What do you think about the infrastructure? What do you imagine the place of your vehicle to be in it under the economical aspect?

Forgot to mention space tethers: They'll never happen either. The complexities of a carrier landing, multiplied a hundred-fold.

I disagree. A carrier landing occurs at high minimum speed, directly into the turbulent wind boiling off the hull (often with poor visibility).

Approach to a tether effective center of mass (the free orbit point) can be leisurely, inching in over days if needed. No wind, no fog, no weather at all. Although both tether and ship are whizzing through space, so are you and your front door. (Over 1000 feet per second in inertial space). Few of us have trouble of achieving the later kind of docking.